High accuracy of relative defect locations for repeater analysis

ABSTRACT

Methods and systems for transforming positions of defects detected on a wafer are provided. One method includes aligning output of an inspection subsystem for a first frame in a first swath in a first die in a first instance of a multi-die reticle printed on the wafer to the output for corresponding frames, swaths, and dies in other reticle instances printed on the wafer. The method also includes determining different swath coordinate offsets for each of the frames, respectively, in the other reticle instances based on the swath coordinates of the output for the frames and the corresponding frames aligned thereto and applying one of the different swath coordinate offsets to the swath coordinates reported for the defects based on the other reticle instances in which they are detected thereby transforming the swath coordinates for the defects from swath coordinates in the other reticle instances to the first reticle instance.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention generally relates to methods and systems for determiningrelative defect locations with relatively high accuracy for repeateranalysis.

2. Description of the Related Art

The following description and examples are not admitted to be prior artby virtue of their inclusion in this section.

Fabricating semiconductor devices such as logic and memory devicestypically includes processing a substrate such as a semiconductor waferusing a large number of semiconductor fabrication processes to formvarious features and multiple levels of the semiconductor devices. Forexample, lithography is a semiconductor fabrication process thatinvolves transferring a pattern from a reticle to a resist arranged on asemiconductor wafer. Additional examples of semiconductor fabricationprocesses include, but are not limited to, chemical-mechanical polishing(CMP), etch, deposition, and ion implantation. Multiple semiconductordevices may be fabricated in an arrangement on a single semiconductorwafer and then separated into individual semiconductor devices.

Inspection processes are used at various steps during a semiconductormanufacturing process to detect defects on wafers to promote higheryield in the manufacturing process and thus higher profits. Inspectionhas always been an important part of fabricating semiconductor devicessuch as ICs. However, as the dimensions of semiconductor devicesdecrease, inspection becomes even more important to the successfulmanufacture of acceptable semiconductor devices because smaller defectscan cause the devices to fail.

Some current inspection methods detect repeater defects on wafers tothereby detect defects on reticles. For example, a reticle is repeatedlyprinted on a wafer in different areas to thereby create multipleinstances of the reticle printed on the wafer. As such, if a defect isdetected repeatedly (“a repeater defect”) at multiple locations on awafer corresponding to the same location on a reticle, the defects maybe caused by the reticle itself. Therefore, repeater defects may beanalyzed to determine if they are caused by reticle defects, rather thansome other cause. A single-die reticle is generally defined as a reticlethat consists of only one die. A multi-die reticle is one that consistsof multiple dies.

In general, repeater defect detection (RDD) is performed as a waferpost-processing (PP) operation. For example, the inspection tool mayperform normal die-to-die defect detection (DD), and after all waferdefects are reported, the RDD may be performed in a post-processing steprather than in a different computer component when the wafer is beingscanned. The repeater defects are defined as defects positioned at thesame relative reticle location (within a certain tolerance) in severalinstances of the reticle printed on the wafer.

In some currently used repeater defect detection methods and systems,such as those performed for multi-die reticles that have been printed onwafers, defects are detected swath-by-swath and defect locations arereported relative to the die or reticle. Such methods and systemsproduce good defect locations within each swath because premap andrun-time alignment (RTA) aligns the dies in the same swath or reticlerow. However, there is not any mechanism to align reticle instancesbetween swaths across reticle-rows. The repeater defect locationsbetween swaths on different reticle instances can be as large as 2× ofswath location accuracy, e.g., about 300 nm or about 10 pixels. Ideally,repeater tolerance should be set equal to or larger than 300 nm to findall repeater instances. A relatively large repeater tolerance causesmore random defects to be detected as repeaters.

Accordingly, it would be advantageous to develop systems and/or methodsfor determining relative defect locations with relatively high accuracyfor repeater analysis that do not have one or more of the disadvantagesdescribed above.

SUMMARY OF THE INVENTION

The following description of various embodiments is not to be construedin any way as limiting the subject matter of the appended claims.

One embodiment relates to a system configured to transform positions ofdefects detected on a wafer. The system includes an inspection subsystemthat includes at least an energy source and a detector. The energysource is configured to generate energy that is directed to a wafer. Thedetector is configured to detect energy from the wafer and to generateoutput responsive to the detected energy. The output includes multipleswaths of frames of output for each of multiple dies on the wafer, andeach of multiple instances of a reticle printed on the wafer includes atleast two instances of the multiple dies.

The system also includes one or more computer subsystems configured fordetecting defects on the wafer by applying a defect detection method tothe output generated by the detector. For single-die reticles, repeaterdefects cannot be detected by any approach with die-to-die comparisonbecause repeater defect signal is canceled out by such comparisons. Adifferent approach can be used for defect detection for single-diereticles. This is not the subject of the embodiments described herein.For multi-die reticles, the repeater defects do not appear in immediateneighboring dies, so die-to-die comparison can be used. Positions of thedefects are reported by the defect detection method in swathcoordinates.

The one or more computer subsystems are also configured for aligning theoutput for a first of the frames in a first of the multiple swaths in afirst of the multiple dies in a first of the multiple instances of thereticle printed on the wafer to the output for corresponding others ofthe frames in corresponding others of the multiple swaths incorresponding others of the multiple dies in others of the multipleinstances of the reticle printed on the wafer. In addition, the one ormore computer subsystems are configured for determining different swathcoordinate offsets for each of the frames, respectively, in the othersof the multiple instances of the reticle based on differences betweenswath coordinates of the output for the frames and swath coordinates ofthe output for the first of the frames aligned thereto in the aligningstep. The one or more computer subsystems are further configured forapplying one of the different swath coordinate offsets to the swathcoordinates reported for the defects detected on the wafer, where whichof the different swath coordinate offsets is applied to the swathcoordinates reported for the defects is determined based on the othersof the multiple instances of the reticle in which the defects weredetected, thereby transforming the swath coordinates reported for thedefects from swath coordinates in the others of the multiple instancesof the reticle to swath coordinates in the first of the multipleinstances of the reticle. The system may be further configured asdescribed herein.

Another embodiment relates to a computer-implemented method fortransforming positions of defects detected on a wafer. The methodincludes steps for each of the functions of the one or more computersubsystems described above. The steps of the method are performed by oneor more computer subsystems coupled to an inspection subsystemconfigured as described above. The method may be performed as describedfurther herein. In addition, the method may include any other step(s) ofany other method(s) described herein. Furthermore, the method may beperformed by any of the systems described herein.

An additional embodiment relates to a non-transitory computer-readablemedium storing program instructions executable on a computer system forperforming a computer-implemented method for transforming positions ofdefects detected on a wafer. The computer-implemented method includesthe steps of the method described above. The computer-readable mediummay be further configured as described herein. The steps of thecomputer-implemented method may be performed as described furtherherein. In addition, the computer-implemented method for which theprogram instructions are executable may include any other step(s) of anyother method(s) described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to theaccompanying drawings in which:

FIGS. 1 and 2 are schematic diagrams illustrating side views ofembodiments of a system configured as described herein;

FIG. 3 is a schematic diagram illustrating a reticle stack view ofexamples of different repeater defect detection results generated fordefects whose defect positions were determined with different defectlocation accuracies;

FIG. 4 is a schematic diagram illustrating a plan view of one example ofinstances of a reticle printed on a wafer and one embodiment of defectcoordinate translation of individual instances of the reticle printed onthe wafer to a first instance of the reticle printed on the wafer;

FIGS. 5 and 7 are schematic diagrams illustrating plan views of oneexample of instances of a reticle printed on a wafer and embodiments ofselecting alignment targets in multiple swaths of one of the instancesof the reticle for use in the embodiments described herein;

FIGS. 6 and 8 are schematic diagrams illustrating plan views of oneexample of instances of a reticle printed on a wafer and embodiments oftransforming swath coordinates reported for defects detected on thewafer from swath coordinates in the instance of the reticle in which thedefects were detected to swath coordinates of a first of the instancesof the reticle printed on the wafer; and

FIG. 9 is a block diagram illustrating one embodiment of anon-transitory computer-readable medium storing program instructionsexecutable on a computer system for performing one or more of thecomputer-implemented methods described herein.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Itshould be understood, however, that the drawings and detaileddescription thereto are not intended to limit the invention to theparticular form disclosed, but on the contrary, the intention is tocover all modifications, equivalents and alternatives falling within thespirit and scope of the present invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings, it is noted that the figures are not drawnto scale. In particular, the scale of some of the elements of thefigures is greatly exaggerated to emphasize characteristics of theelements. It is also noted that the figures are not drawn to the samescale. Elements shown in more than one figure that may be similarlyconfigured have been indicated using the same reference numerals. Unlessotherwise noted herein, any of the elements described and shown mayinclude any suitable commercially available elements.

One embodiment relates to a system configured to transform positions ofdefects detected on a wafer. The embodiments described herein areparticularly suitable for detecting repeater defects on a wafer that arecaused by a multi-die reticle printed on the wafer. For multi-diereticles, the die and reticle coordinate transformation is known andfixed for all die-rows. If a defect die location is determined, itsreticle location can be calculated. In general, the embodimentsdescribed herein are configured for determining accurate (orsubstantially accurate) relative defect locations for repeater analysis.More particularly, the embodiments described herein generally transformdefect locations from all reticle instances printed on a wafer to commoncoordinates during inspection and significantly increase relative defectlocation accuracy. The embodiments described herein can help to reducethe false repeater defect count for repeater analysis. The multi-diereticle can be any multi-die reticle known in the art. The wafer mayinclude any wafer known in the art.

One embodiment of such a system is shown in FIG. 1. The system includesan inspection subsystem that includes at least an energy source and adetector. The energy source is configured to generate energy that isdirected to a wafer. The detector is configured to detect energy fromthe wafer and to generate output responsive to the detected energy.

In one embodiment, the energy directed to the wafer includes light, andthe energy detected from the wafer includes light. For example, in theembodiment of the system shown in FIG. 1, inspection subsystem 10includes an illumination subsystem configured to direct light to wafer14. The illumination subsystem includes at least one light source. Forexample, as shown in FIG. 1, the illumination subsystem includes lightsource 16. In one embodiment, the illumination subsystem is configuredto direct the light to the wafer at one or more angles of incidence,which may include one or more oblique angles and/or one or more normalangles. For example, as shown in FIG. 1, light from light source 16 isdirected through optical element 18 and then lens 20 to beam splitter21, which directs the light to wafer 14 at a normal angle of incidence.The angle of incidence may include any suitable angle of incidence,which may vary depending on, for instance, characteristics of the waferand the defects to be detected on the wafer.

The illumination subsystem may be configured to direct the light to thewafer at different angles of incidence at different times. For example,the inspection subsystem may be configured to alter one or morecharacteristics of one or more elements of the illumination subsystemsuch that the light can be directed to the wafer at an angle ofincidence that is different than that shown in FIG. 1. In one suchexample, the inspection subsystem may be configured to move light source16, optical element 18, and lens 20 such that the light is directed tothe wafer at a different angle of incidence.

In some instances, the inspection subsystem may be configured to directlight to the wafer at more than one angle of incidence at the same time.For example, the illumination subsystem may include more than oneillumination channel, one of the illumination channels may include lightsource 16, optical element 18, and lens 20 as shown in FIG. 1 andanother of the illumination channels (not shown) may include similarelements, which may be configured differently or the same, or mayinclude at least a light source and possibly one or more othercomponents such as those described further herein. If such light isdirected to the wafer at the same time as the other light, one or morecharacteristics (e.g., wavelength, polarization, etc.) of the lightdirected to the wafer at different angles of incidence may be differentsuch that light resulting from illumination of the wafer at thedifferent angles of incidence can be discriminated from each other atthe detector(s).

In another instance, the illumination subsystem may include only onelight source (e.g., source 16 shown in FIG. 1) and light from the lightsource may be separated into different optical paths (e.g., based onwavelength, polarization, etc.) by one or more optical elements (notshown) of the illumination subsystem. Light in each of the differentoptical paths may then be directed to the wafer. Multiple illuminationchannels may be configured to direct light to the wafer at the same timeor at different times (e.g., when different illumination channels areused to sequentially illuminate the wafer). In another instance, thesame illumination channel may be configured to direct light to the waferwith different characteristics at different times. For example, in someinstances, optical element 18 may be configured as a spectral filter andthe properties of the spectral filter can be changed in a variety ofdifferent ways (e.g., by swapping out the spectral filter) such thatdifferent wavelengths of light can be directed to the wafer at differenttimes. The illumination subsystem may have any other suitableconfiguration known in the art for directing light having different orthe same characteristics to the wafer at different or the same angles ofincidence sequentially or simultaneously.

In one embodiment, light source 16 may include a broadband plasma (BBP)light source. In this manner, the light generated by the light sourceand directed to the wafer may include broadband light. However, thelight source may include any other suitable light source such as alaser. The laser may include any suitable laser known in the art and maybe configured to generate light at any suitable wavelength orwavelengths known in the art. In addition, the laser may be configuredto generate light that is monochromatic or nearly-monochromatic. In thismanner, the laser may be a narrowband laser. The light source may alsoinclude a polychromatic light source that generates light at multiplediscrete wavelengths or wavebands.

Light from optical element 18 may be focused to beam splitter 21 by lens20. Although lens 20 is shown in FIG. 1 as a single refractive opticalelement, it is to be understood that, in practice, lens 20 may include anumber of refractive and/or reflective optical elements that incombination focus the light from the optical element to the wafer. Theillumination subsystem shown in FIG. 1 and described herein may includeany other suitable optical elements (not shown). Examples of suchoptical elements include, but are not limited, to, polarizingcomponent(s), spectral filter(s), spatial filter(s), reflective opticalelement(s), apodizer(s), beam splitter(s), aperture(s), and the like,which may include any such suitable optical elements known in the art.In addition, the system may be configured to alter one or more of theelements of the illumination subsystem based on the type of illuminationto be used for inspection.

The inspection subsystem may also include a scanning subsystemconfigured to cause the light to be scanned over the wafer. For example,the inspection subsystem may include stage 22 on which wafer 14 isdisposed during inspection. The scanning subsystem may include anysuitable mechanical and/or robotic assembly (that includes stage 22)that can be configured to move the wafer such that the light can bescanned over the wafer. In addition, or alternatively, the inspectionsubsystem may be configured such that one or more optical elements ofthe inspection subsystem perform some scanning of the light over thewafer. The light may be scanned over the wafer in any suitable fashion.

The inspection subsystem further includes one or more detectionchannels. At least one of the one or more detection channels includes adetector configured to detect light from the wafer due to illuminationof the wafer by the inspection subsystem and to generate outputresponsive to the detected light. For example, the inspection subsystemshown in FIG. 1 includes two detection channels, one formed by collector24, element 26, and detector 28 and another formed by collector 30,element 32, and detector 34. As shown in FIG. 1, the two detectionchannels are configured to collect and detect light at different anglesof collection. In some instances, one detection channel is configured todetect specularly reflected light, and the other detection channel isconfigured to detect light that is not specularly reflected (e.g.,scattered, diffracted, etc.) from the wafer. However, two or more of thedetection channels may be configured to detect the same type of lightfrom the wafer (e.g., specularly reflected light). Although FIG. 1 showsan embodiment of the inspection subsystem that includes two detectionchannels, the inspection subsystem may include a different number ofdetection channels (e.g., only one detection channel or two or moredetection channels). Although each of the collectors are shown in FIG. 1as single refractive optical elements, it is to be understood that eachof the collectors may include one or more refractive optical elements)and/or one or more reflective optical element(s).

The one or more detection channels may include any suitable detectorsknown in the art. For example, the detectors may includephoto-multiplier tubes (PMTs), charge coupled devices (CCDs), and timedelay integration (TDI) cameras. The detectors may also include anyother suitable detectors known in the art. The detectors may alsoinclude non-imaging detectors or imaging detectors. In this manner, ifthe detectors are non-imaging detectors, each of the detectors may beconfigured to detect certain characteristics of the scattered light suchas intensity but may not be configured to detect such characteristics asa function of position within the imaging plane. As such, the outputthat is generated by each of the detectors included in each of thedetection channels of the inspection subsystem may be signals or data,but not image signals or image data. In such instances, a computersubsystem such as computer subsystem 36 of the system may be configuredto generate images of the wafer from the non-imaging output of thedetectors. However, in other instances, the detectors may be configuredas imaging detectors that are configured to generate imaging signals orimage data. Therefore, the system may be configured to generate theoutput described herein in a number of ways.

It is noted that FIG. 1 is provided herein to generally illustrate aconfiguration of an inspection subsystem that may be included in thesystem embodiments described herein. Obviously, the inspection subsystemconfiguration described herein may be altered to optimize theperformance of the system as is normally performed when designing acommercial inspection system. In addition, the systems described hereinmay be implemented using an existing inspection system (e.g., by addingfunctionality described herein to an existing inspection system) such asthe 29xx/39xx and Puma 9xxx series of tools that are commerciallyavailable from KLA-Tencor. For some such systems, the methods describedherein may be provided as optional functionality of the system (e.g., inaddition to other functionality of the system). Alternatively, thesystem described herein may be designed “from scratch” to provide acompletely new system.

Computer subsystem 36 of the system may be coupled to the detectors ofthe inspection subsystem in any suitable manner (e.g., via one or moretransmission media, which may include “wired” and/or “wireless”transmission media) such that the computer subsystem can receive theoutput generated by the detectors during scanning of the wafer. Computersubsystem 36 may be configured to perform a number of functions usingthe output of the detectors as described herein and any other functionsdescribed further herein. This computer subsystem may be furtherconfigured as described herein.

This computer subsystem (as well as other computer subsystems describedherein) may also be referred to herein as computer system(s). Each ofthe computer subsystem(s) or system(s) described herein may take variousforms, including a personal computer system, image computer, embeddedsystem, mainframe computer system, workstation, network appliance,Internet appliance, or other device. In general, the term “computersystem” may be broadly defined to encompass any device having one ormore processors, which executes instructions from a memory medium. Thecomputer subsystem(s) or system(s)) may also include any suitableprocessor known in the art such as CPU and GPU. In addition, thecomputer subsystem(s) or system(s) may include a computer platform withhigh speed processing and software, either as a standalone or anetworked tool.

If the system includes more than one computer subsystem, then thedifferent computer subsystems may be coupled to each other such thatimages, data, information, instructions, etc. can be sent between thecomputer subsystems as described further herein. For example, computersubsystem 36 may be coupled to computer subsystem(s) 102 (as shown bythe dashed line in FIG. 1) by any suitable transmission media, which mayinclude any suitable wired and/or wireless transmission media known inthe art. Two or more of such computer subsystems may also be effectivelycoupled by a shared computer-readable storage medium (not shown).

Although the inspection subsystem is described above as being an opticalor light-based inspection subsystem, the inspection subsystem may be anelectron beam-based inspection subsystem. For example, in oneembodiment, the energy directed to the wafer includes electrons, and theenergy detected from the wafer includes electrons. In this manner, theenergy source may be an electron beam source. In one such embodimentshown in FIG. 2, the inspection subsystem includes electron column 122,which is coupled to computer subsystem 124.

As also shown in FIG. 2, the electron column includes electron beamsource 126 configured to generate electrons that are focused to wafer128 by one or more elements 130. The electron beam source may include,for example, a cathode source or emitter tip, and one or more elements130 may include, for example, a gun lens, an anode, a beam limitingaperture, a gate valve, a beam current selection aperture, an objectivelens, and a scanning subsystem, all of which may include any suchsuitable elements known in the art.

Electrons returned from the wafer (e.g., secondary electrons) may befocused by one or more elements 132 to detector 134. One or moreelements 132 may include, for example, a scanning subsystem, which maybe the same scanning subsystem included in element(s) 130.

The electron column may include any other suitable elements known in theart. In addition, the electron column may be further configured asdescribed in U.S. Pat. No. 8,664,594 issued Apr. 4, 2014 to Jiang etal., U.S. Pat. No. 8,692,204 issued Apr. 8, 2014 to Kojima et al., U.S.Pat. No. 8,698,093 issued Apr. 15, 2014 to Gubbens et al., and U.S. Pat.No. 8,716,662 issued May 6, 2014 to MacDonald et al., which areincorporated by reference as if fully set forth herein.

Although the electron column is shown in FIG. 2 as being configured suchthat the electrons are directed to the wafer at an oblique angle ofincidence and are scattered from the wafer at another oblique angle, itis to be understood that the electron beam may be directed to andscattered from the wafer at any suitable angles. In addition, theelectron beam-based subsystem may be configured to use multiple modes togenerate images of the wafer (e.g., with different illumination angles,collection angles, etc.). The multiple modes of the electron beam-basedsubsystem may be different in any image generation parameters of thesubsystem.

Computer subsystem 124 may be coupled to detector 134 as describedabove. The detector may detect electrons returned from the surface ofthe wafer thereby forming electron beam images of the wafer. Theelectron beam images may include any suitable electron beam images.Computer subsystem 124 may be configured to perform any of the functionsdescribed herein using the output of the detector and/or the electronbeam images. Computer subsystem 124 may be configured to perform anyadditional step(s) described herein. A system that includes theinspection subsystem shown in FIG. 2 may be further configured asdescribed herein.

It is noted that FIG. 2 is provided herein to generally illustrate aconfiguration of an electron beam-based inspection subsystem that may beincluded in the embodiments described herein. As with the opticalinspection subsystem described above, the electron beam-based inspectionsubsystem configuration described herein may be altered to optimize theperformance of the inspection subsystem as is normally performed whendesigning a commercial inspection system. In addition, the systemsdescribed herein may be implemented using an existing inspection system(e.g., by adding functionality described herein to an existinginspection system) such as the eSxxx series of tools that arecommercially available from KLA-Tencor. For some such systems, themethods described herein may be provided as optional functionality ofthe system (e.g., in addition to other functionality of the system).Alternatively, the system described herein may be designed “fromscratch” to provide a completely new system.

Although the inspection subsystem is described above as being alight-based or electron beam-based inspection subsystem, the inspectionsubsystem may be an ion beam-based inspection subsystem. Such aninspection subsystem may be configured as shown in FIG. 2 except thatthe electron beam source may be replaced with any suitable ion beamsource known in the art. In addition, the inspection subsystem may beany other suitable ion beam-based subsystem such as those included incommercially available focused ion beam (FIB) systems, helium ionmicroscopy (HIM) systems, and secondary ion mass spectroscopy (SIMS)systems.

As noted above, the optical and electron beam inspection subsystems maybe configured for directing energy (e.g., light, electrons) to and/orscanning energy over a physical version of the wafer thereby generatingactual (i.e., not simulated) output and/or images for the physicalversion of the wafer. In this manner, the optical and electron beaminspection subsystems may be configured as “actual” tools, rather than“virtual” tools. Computer subsystem(s) 102 shown in FIG. 1 may, however,include one or more “virtual” systems (not shown) that are configuredfor performing one or more functions using at least some of the actualoptical images and/or the actual electron beam images generated for thewater, which may include any of the one or more functions describedfurther herein.

The one or more virtual systems are not capable of having the waferdisposed therein. In particular, the virtual system(s) are not part ofoptical inspection subsystem 10 or electron beam inspection subsystem122 and do not have any capability for handling the physical version ofthe wafer. In other words, in a system configured as a virtual system,the output of its one or more “detectors” may be output that waspreviously generated by one or more detectors of an actual inspectionsubsystem and that is stored in the virtual system, and during the“imaging and/or scanning,” the virtual system may replay the storedoutput as though the wafer is being imaged and/or scanned. In thismanner, imaging and/or scanning the water with a virtual system mayappear to be the same as though a physical wafer is being imaged and/orscanned with an actual system, while, in reality, the “imaging and/orscanning” involves simply replaying output for the wafer in the samemanner as the wafer may be imaged and/or scanned.

Systems and methods configured as “virtual” inspection systems aredescribed in commonly assigned U.S. Pat. No. 8,126,255 issued on Feb.28, 2012 to Bhaskar et al. and U.S. Pat. No. 9,222,895 issued on Dec.29, 2015 to Duffy et al., both of which are incorporated by reference asif fully set forth herein. The embodiments described herein may befurther configured as described in these patents. For example, the oneor more computer subsystems described herein may be further configuredas described in these patents.

The inspection subsystems described herein may be configured to generateoutput for the wafer with multiple modes or “different modalities.” Ingeneral, a “mode” or “modality” (as those terms are used interchangeablyherein) of an inspection subsystem can be defined by the values ofparameters of the inspection subsystem used for generating output and/orimages for a wafer. Therefore, modes that are different may be differentin the values for at least one of the parameters of the inspectionsubsystem. In this manner, in some embodiments, the optical imagesinclude images generated by the optical inspection subsystem with two ormore different values of a parameter of the optical inspectionsubsystem. For example, in one embodiment of an optical inspectionsubsystem, at least one of the multiple modes uses at least onewavelength of the light for illumination that is different from at leastone wavelength of the light for illumination used for at least one otherof the multiple modes. The modes may be different in the illuminationwavelength as described further herein (e.g., by using different lightsources, different spectral filters, etc.) for different modes. Inanother embodiment, at least one of the multiple modes uses anillumination channel of the optical inspection subsystem that isdifferent from an illumination channel of the optical inspectionsubsystem used for at least one other of the multiple modes. Forexample, as noted above, the optical inspection subsystem may includemore than one illumination channel. As such, different illuminationchannels may be used for different modes.

In a similar manner, the electron beam images may include imagesgenerated by the electron beam inspection subsystem with two or moredifferent values of a parameter of the electron beam inspectionsubsystem. For example, the electron beam inspection subsystem may beconfigured to generate output for the wafer with multiple modes or“different modalities.” The multiple modes or different modalities ofthe electron beam inspection subsystem can be defined by the values ofparameters of the electron beam inspection subsystem used for generatingoutput and/or images for a wafer. Therefore, modes that are differentmay be different in the values for at least one of the electron beamparameters of the inspection subsystem. For example, in one embodimentof an electron beam inspection subsystem, at least one of the multiplemodes uses at least one angle of incidence for illumination that isdifferent from at least one angle of incidence of the illumination usedfor at least one other of the multiple modes.

The output of the detector generated for the wafer includes multipleswaths of frames of output for each of multiple dies on the wafer, andeach of multiple instances of a reticle printed on the wafer includes atleast two instances of the multiple dies. For example, regardless ofwhether the detector(s) of the inspection subsystem produce signalsand/or images, a “frame” may be generally defined as a relatively smallportion of output (e.g., signals or image portions (e.g., pixels))generated by an inspection subsystem that can be collectively processedas a unit by the system. Therefore, a “frame” of output can varydepending on the inspection subsystem configuration as well as theconfiguration of any components included in the system for handlingand/or processing of the output generated by the inspection subsystem. Aswath or a sub-swath of output generated for a wafer may be divided intomultiple frames such that data handling and processing of the frames canbe performed much more easily than if the entire swath or subswath ofoutput is processed simultaneously. In addition, inspection generallydivides a die or a reticle instance printed on a wafer into multipleswaths vertically as shown in figures described further herein.

The one or more computer subsystems are configured for detecting defectson the wafer by applying a defect detection method to the outputgenerated by the detector. The defect detection method may be applied tothe output in any suitable manner, and the defect detection method mayinclude any suitable defect detection method known in the art. Thedefect detection method may include, for example, comparing the outputto a threshold (a defect detection threshold) and the output that hasone or more values above the threshold is determined to correspond todefects while the output that does not have one or more values above thethreshold is not determined to correspond to defects. Applying thedefect detection method to the output may also include applying anyanother defect detection method and/or algorithm to the output.

Positions of the defects are reported by the defect detection method inswath coordinates. For example, the defect detection method may generateresults of applying the defect detection method to the output. Theresults may include at least a position of each defect and any othersuitable information such as a defect ID, defect information (e.g.,size) determined by the defect detection method, and the like. Thedefect detection method may be configured such that the defect positionsare reported in swath coordinates. In other words, the defect positionsthat are reported for the defects may be in-swath positions or swathrelative positions. In one such example, the swath coordinates for thedefects may be determined relative to an origin (or other referencepoint) of the swath in which they were detected. In a particularexample, each swath image can be viewed as a normal image. The top leftcorner of the normal image can be used as the origin of the swath in onesuch example. The swath coordinates of the defects may then bedetermined with respect to the top left corner of the swath. In thismanner, the swath coordinates of the defects are determined with respectto the swath in which they are detected but are not determined withrespect to the wafer being inspected. Locations of defects of a repeatermay be different in different swaths because swath offsets to the waferare different due to stage uncertainty. The embodiments described hereincan effectively eliminate those differences as described further herein.

The one or more computer subsystems are configured for aligning theoutput for a first of the frames in a first of the multiple swaths in afirst of the multiple dies in a first of the multiple instances of thereticle printed on the wafer to the output for corresponding others ofthe frames in corresponding others of the multiple swaths incorresponding others of the multiple dies in others of the multipleinstances of the reticle printed on the wafer. In this manner, theoutput for corresponding frames of corresponding swaths in correspondingdies in different reticle instances printed on the wafer may be alignedto each other. In other words, the output for the first frame of thefirst swath of the first of the multiple dies in the first of themultiple instances of the reticle printed on the wafer may be aligned tothe output for the corresponding frames of the corresponding swaths ofthe corresponding dies in other reticle instances printed on the wafer.

Aligning the output in one frame to its corresponding output in anotherframe as described above may be performed in any suitable manner. Forexample, in one embodiment, the aligning includes target-based alignmentof the output for the first of the frames to the output for thecorresponding others of the frames. In one such example, the aligningmay be performed using alignment target(s) in the first frame (which maybe selected as described further herein) and corresponding alignmentsites in corresponding frames, and aligning the output for the alignmentsites to the output generated for the alignment target may includepattern matching, matching one or more characteristics (e.g., acentroid, pattern edges, etc.) of the different output, etc. In otherwords, the embodiments described herein are not limited in the aligningthat may be performed for the alignment sites and targets.

In another embodiment, the aligning includes feature-based alignment ofthe output for the first of the frames to the output for thecorresponding others of the frames. The features that are used for thisalignment may include patterned features in a design for the wafer,patterned features in images generated for the wafer by the inspectionsubsystem (which may or may not correspond to features on the wafer),features of patterns on the wafer such as edges, centroids, corners,structures, etc. of the patterns, and the like. Such alignment may beperformed in any suitable manner. For example, such aligning may includefeature matching (e.g., edge matching), which may be performed in anysuitable manner known in the art.

In an additional embodiment, the aligning includes normalized crosscorrelation (NCC)-based alignment of the output for the first of theframes to the output for the corresponding others of the frames. Thealigning may be performed using any suitable NCC method and/or algorithmknown in the art. In a further embodiment, the aligning includes FastFourier transform (FFT)-based alignment of the output for the first ofthe frames to the output for the corresponding others of the frames. Thealigning may be performed using any suitable FFT method and/or algorithmknown in the art. In some embodiments, the aligning includes sum ofsquared difference (SSD)-based alignment of the output for the first ofthe frames to the output for the corresponding others of the frames. Thealigning may be performed using any suitable SSD method and/or algorithmknown in the art.

The one or more computer subsystems are further configured fordetermining different swath coordinate offsets for each of the frames,respectively, in the others of the multiple instances of the reticlebased on differences between swath coordinates of the output for theframes and swath coordinates of the output for the first of the framesaligned thereto in the aligning step. In this manner, a swath coordinateoffset may be separately and independently determined for each frame andeach swath in each of the dies in each of the instances of the reticleprinted on the wafer with respect to its corresponding frame. The swathcoordinate offsets may be determined in any suitable manner based on theoutput in the frames that is aligned to the output for the first frameand their corresponding swath coordinates, respectively. The swathcoordinate offsets may have any suitable format (e.g., a function orformula). In addition, information for the swath coordinate offsets maybe stored in any suitable storage media described herein. Furthermore,the swath coordinate offsets may be determined in one only direction(e.g., the x or the y direction) or in two directions (e.g., the x and ydirections). Moreover, the swath coordinate offsets may be determinedusing swath coordinates having any suitable format (e.g., polar andCartesian coordinates).

The one or more computer subsystems are also configured for applying oneof the different swath coordinate offsets to the swath coordinatesreported for the defects detected on the wafer, where which of thedifferent swath coordinate offsets is applied to the swath coordinatesreported for the defects is determined based on the others of themultiple instances of the reticle in which the defects were detected,thereby transforming the swath coordinates reported for the defects fromswath coordinates in the others of the multiple instances of the reticleto swath coordinates in the first of the multiple instances of thereticle. The frame, swath, die, and reticle instance in which a defectis detected may be determined based on the swath coordinates determinedby the defect detection method for the defect. Based on the frame,swath, die, and printed reticle instance in which a defect is detected,the corresponding swath coordinate offset may be determined (because itis known which swath coordinate offset was determined for which frame,swath, die, and reticle instance and it is known which reticle instanceeach defect was detected in, that knowledge can be used to determine theappropriate swath coordinate offset based on the swath coordinates ofthe defects). That identified swath coordinate offset may then beapplied to the swath coordinates determined for the defect therebytransforming the swath coordinates of the defect from the swathcoordinates in the reticle instance in which it was detected to theswath coordinates in the first reticle instance. This swath coordinatetransform process may be separately and independently performed for eachdefect detected on the wafer (or as many of the detected defects asdesired). The swath coordinate offsets may be applied to the swathcoordinates reported for the defects in any suitable manner.

FIG. 4 illustrates the general concept of the transforming stepdescribed above. In particular, FIG. 4 shows the defect swath coordinatetranslation of individual reticle instances to a first inspected reticleinstance. In this instance, wafer 400 includes a number of reticleinstances formed thereon, and which include reticle instances 402 and404. In the example shown in FIG. 4, reticle instance 404 may be used asthe first inspected reticle instance, and locations of defects detectedin reticle instance 402 may transformed to swath coordinates of reticleinstance 404. In particular, as described above, the applying step mapsdefect locations into the swath coordinates of the first reticleinstance by applying a swath coordinate transformation between the firstand other reticle instances on the wafer. All defect locationstransformed as described herein into the first reticle instance/swathcoordinates are substantially accurate. As such, defects for eachrepeater are much closer than currently used inspection performedwithout this feature. In particular, in currently used inspection, sincethe swaths are not registered or aligned to each other, defects of onerepeater can be relatively far from each other on a reticle stack. Incontrast, in the embodiments described herein, all other reticleinstances are registered to the first reticle instance and then defectlocations from the other reticle instances are accurately mapped to thefirst reticle instance. Since the mapping is substantially accurate,defects of one repeater are mapped to the first reticle instance and aresubstantially close to one another.

Although one particular reticle instance (reticle instance 404) is shownin FIG. 4 (and other figures described herein) as being used as thefirst of the multiple reticle instances, the reticle instance that isused as the first of the multiple reticle instances may be differentfrom that shown herein. In general, any reticle instance on the waferthat is scanned by the inspection subsystem (thereby generating outputfor the reticle instance) may be used as the first of the multiplereticle instances. In some instances, it may be practical to use thefirst reticle instance that is scanned as the first of the multiplereticle instances. However, any appropriate reticle instance may be usedas the first reticle instance for the embodiments described herein.

In this manner, the embodiments described herein determine relativedefect positions (or relative defect locations) with substantially highaccuracy. As further described herein, the defect positions aretransformed from swath coordinates of one reticle instance to swathcoordinates of another reticle instance. Therefore, the relative defectpositions are determined herein with respect to different swaths in onereticle instance. As such, the relative defect positions determined asdescribed herein are different from absolute defect positions, which aregenerally defined as the defect positions relative to the wafercoordinates. In this manner, the relative defect location accuracy ofthe embodiments described herein is the accuracy relative to swathcoordinates.

In one embodiment, the one or more computer subsystems are configuredfor performing the aligning, determining, and applying steps describedabove without design information for devices being formed on the wafer.For example, the embodiments described herein improve defect locationaccuracy relative to a specific reticle instance (the first reticleinstance) and swath without design information for any multi-die reticleinspection, With respect to a multi-die reticle, a reticle is a mask. Adie is a chip. If a mask includes one chip, it is a single die reticle.If a mask includes multiple chips, e.g., 3 chips, it is a multi-diereticle.

In another embodiment, the one or more computer subsystems are notconfigured to perform any steps using design information for devicesbeing formed on the wafer. For example, as described above, thealigning, determining, and applying steps are performed without designinformation in one embodiment. In addition, no other of the stepsdescribed herein may be performed using design information. Therefore,the embodiments described herein can be performed regardless of whetheror not design information is available for use in the systems andmethods described herein.

In one embodiment, the wafer is printed with a multi-die reticle priorto the detecting. For example, the embodiments described herein may beused for detecting defects on multi-die reticles by detecting defects onwafers that were printed with the multi-die reticles and thendetermining which of the defects detected on the wafers are due to themulti-die reticles. Determining which of the defects detected on thewafers are due to the multi-die reticles may be performed by identifyingrepeating defects or “repeaters” on the wafers. In this manner, thedefects detected on the wafers that are due to multi-die reticles usedto print the wafers may be identified by repeater analysis, which may beperformed as described further herein.

In some embodiments, the one or more computer subsystems are configuredfor determining if the defects are repeater defects based on thetransformed swath coordinates for the defects. In this manner, theembodiments described herein may be configured to perform repeateranalysis to determine which of the defects are repeaters. Repeaters aregenerally defined as a set of defects (e.g., two or more) that appear atthe “same” reticle instance coordinates (where reticle instancecoordinates can be considered to be the “same” if they are exactly thesame or the same within some predetermined allowable tolerance). Inaddition, defects of a repeater are located on the same correspondingswaths (the same swath in multiple reticle instances) in fixed swathscanning. (In fixed swath scanning, a reticle instance image is acquiredby a scan of multiple sub-die images or swath images. On a wafer, thereare many die rows, Locations of corresponding swath images are the samefor each die row. In other words, each die row is scanned with the sameswath layout.) Repeater analysis is performed to find repeaters from alldetected events.

As described further herein, by transforming the defect positions fromswath coordinates in the reticle instances in which the defects weredetected to swath coordinates of only one of the reticle instances onthe wafer, the defect locations relative to a specific reticle instanceand swath can be determined with substantially high accuracy. If defectlocations relative to the swath in which they are located are moreaccurate, repeater analysis can use a smaller repeater tolerance and canthereby produce fewer false repeaters and reduce the repeater detectiontime. As such, the embodiments described herein allow the repeatersearch area to be reduced by 100× to 10,000× (or repeater tolerance by10×, 10 pixels to 1 pixel for 100× area reduction, 10 pixels to 0.1pixel for 10,000× area reduction) in repeater analysis. “Repeatertolerance” as that term is used herein is defined as the radius centeredat a defect location. Repeater search range would be [−radius, +radius]approximately. The search area is the square of radius times π. Thesmallest search range in pixels is from [−0.1, 0.1] to [−1, 1] dependingon the number of alignment targets that can be identified (or theaccuracy of alignment that is performed in the aligning step). Thesmallest search area is from 0.0314 pixel squared to 3.14 pixel squaredcompared to 314 pixel squared. Reducing the repeater search area in thismanner will potentially reduce false repeaters significantly.

FIG. 3 illustrates how reducing the repeater search area will reducefalse repeater detection. In general, as described with respect to thisfigure, there is a relationship between defect location accuracy,repeater tolerance, and false repeater detection, and the relativedefect location accuracy has an impact on repeater detection. A repeatertolerance is a user-defined parameter which determines the repeatersearch area. A reticle stack is a view of defects on a number of alignedreticle instances superimposed together. All defects within a repeatersearch area on a reticle stack are considered as repeater defectsbelonging to a unique repeater. Unique repeaters are distinguished bytheir reticle coordinates. In one such example, a repeater defectdetection algorithm may determine that if defects are detected in atleast three reticle instances within a repeater search area, those threedefects may be identified as repeaters.

In reticle stack view 300 shown in FIG. 3, defects 304 and 306 areshown. Defects 304 are multiple instances of nuisance defects, anddefects 306 are multiple instances of defects of interest (DOIs). Inparticular, defects 304, shown by the lighter shading in FIG. 3, areknown to be non-repeating defects and defects 306, shown by the darkershading in FIG. 3, are known to be repeating defects. The defects shownin FIG. 3 are not meant to show any actual detects detected on anyactual wafer. Instead, these detects are merely shown in FIG. 3 topromote understanding of the embodiments described herein.

Reticle stack view 300 can be generated in any suitable manner, forinstance, by overlaying information for defects detected in multiplereticle instances printed on a wafer. The information that is overlaidmay include locations at which the defects were located, and the defectsmay be indicated at their locations in the reticle stack view by somesymbol such as the shaded circles shown in FIG. 3. In this manner,defects that have spatial coincidence with each other in multiplereticle instances can be identified in the reticle stack view. In otherwords, defects that are detected at the same or substantially the samelocations in the multiple reticle instances can be identified in thereticle stack view.

The repeater search area may be set based on the relative defectlocation accuracy of the defects being analyzed for repeaters. Inparticular, a larger repeater search area may be used when the relativedefect location accuracy is lower, and a smaller repeater search areamay be used when the relative defect location accuracy is higher. Inthis manner, the repeater search area may be different based on relativedefect location accuracy so that repeaters can be identified regardlessof the accuracy with which the locations have been determined. As shownin FIG. 3, if repeater search area 308 is set large enough so that itcorrectly identifies defects 306 as repeaters, the same repeater searcharea will also incorrectly identify some of defects 304 as repeaters. Inthis manner, due to relatively poor relative defect location accuracy ofthe defects detected in reticle stack view 300, a larger repeatertolerance is used and a false repeater is detected.

However, if the defect relative location accuracy is higher, therepeater defects are spatially closer and non-repeater defects are stilldistributed randomly. The repeater search area can be reduced whilestill correctly identifying repeating defects as such, then the numberof non-repeating defects that are incorrectly identified as repeaterscan be reduced. For instance, as shown in reticle stack view 302, whichcan be generated as described above, defects 304 and 306 are shown. Aswith reticle stack view 300, in reticle stack view 302, defects 304 areknown to be non-repeating defects, and defects 306 are known to berepeating defects. When defect location accuracy is higher, then asmaller repeater search area can be used for repeater analysis of thereticle stack view. If repeater search area 310 having a smaller areathan repeater search area 308 is able to be used in reticle stack view302 because the relative defect locations were determined with greateraccuracy as described herein, then defects 306 can be correctlyidentified as repeating defects without incorrectly identifying any ofdefects 304 as repeating defects. For example, as shown in FIG. 3, eventhe three most closely spaced of defects 304 are not all within repeatersearch area 310 and thus will not be identified as repeater defects. Inthis manner, by reducing the repeater search area, the number of defectsthat are incorrectly determined to be repeaters can be reduced.

In contrast to the embodiments described herein, the currently usedmethods and systems for inspection of wafers printed with multi-diereticles is to detect defects swath-by-swath and report defect locationsrelative to the wafer. This approach produces good defect locations oneach swath because premap and run-time alignment (RTA) align reticleinstances in the same swath or reticle row. However, there is not anymechanism to align reticle instances between swaths across reticle rows.The repeater defect locations between swaths on different reticleinstances can be as large as 2× of swath location accuracy, e.g., about300 nm or about 10 pixels. Ideally, in such situations, repeatertolerance should be set to equal to or larger than 300 nm to find allrepeater instances. However, such a large repeater tolerance causes morerandom defects to be detected as repeaters.

As described further herein, the embodiments described herein determinerelative defect positions or locations with substantially high accuracy.In contrast, absolute defect location accuracy or defect locationaccuracy (DLA), as that term is commonly used in the art, is theaccuracy relative to the wafer coordinates. However, absolute DLA is notnecessary and defect location accuracy relative to a commonreticle-swath coordinate is sufficient for repeater analysis. Morerandom events can be removed (i.e., eliminated as being not repeaterdefects) if defect locations are more accurate in a reticle stack wherereticle location relative to the wafer are not considered. If defectlocations relative to their reticle instance coordinates are moreaccurate, repeater analysis can use a smaller repeater tolerance andproduces fewer false repeaters.

It is also noted that the embodiments described herein focus on methodsand systems that detect defects with substantially high relativelocation accuracy. Repeater analysis may or may not be performed by theembodiments described herein. For example, the substantially highrelative location accuracy of the defect positions determined by theembodiments described herein provide advantages for repeater detectionregardless of how it is performed. In other words, the embodimentsdescribed herein provide substantially accurate defect relativepositions that can then be used in any repeater detection process. Inthis manner, the embodiments described herein can be used with anyrepeater analysis method or system in that the results of thetransformed relative defect positions produced by the embodimentsdescribed herein can be input to any repeater analysis method or system.In addition, the substantially high accuracy relative defect positionsproduced by the embodiments described herein provide advantages forrepeater analysis regardless of how the repeater analysis is performed.

In another embodiment, the one or more computer subsystems areconfigured for determining if the defects are caused on the wafer by thereticle used to print patterned features on the wafer based on thetransformed swath coordinates for the defects. In one such embodiment,the reticle is an extreme ultraviolet (EUV) reticle. For example, theembodiments described herein can be used for print check for EUV maskmonitoring, which is performed to detect repeaters periodically duringwafer production. In other words, determining if the defects are causedon the wafer by the reticle may include performing repeater analysis asdescribed above and then possibly examining the detected repeaters todetermine if they correspond to some feature or defect on the reticle.As described further herein, the embodiments are particularly suitablefor detection of repeating defects on wafers printed with multi-diereticles. In addition, the embodiments described herein are particularlysuitable for detection of repeating defects on wafers caused by EUVreticles (that is, reticles designed for use in EUV lithographyperformed with EUV light). Because such reticles do not includeprotective pellicles, they are more susceptible to contamination thatoccurs during lithography processes. As such, these reticles tend toneed to be examined at regular intervals to determine if they are stillsuitable for use in lithography processes. The embodiments describedherein provide methods and systems that are particularly suitable forsuch reticle examination.

In an additional embodiment, the output for the first of the frames usedin the aligning step is output for an alignment target in the first ofthe frames, the output, for the corresponding others of the frames usedin the aligning step is output for alignment sites in the correspondingothers of the frames, the computer subsystem(s) are configured forselecting alignment targets in the frames in the first of the multipleswaths in the first of the multiple instances of the reticle, andselecting the alignment targets includes selecting at least one of thealignment targets in each of the frames in the first of the multipleswaths in the first of the multiple instances of the reticle. In otherwords, at least one alignment target may be selected in each of theframes in a swath in the reticle instance that will be used as the firstreticle instance. Such alignment target selection may be performed foreach swath that will be scanned on the wafer. In this manner, at leastone alignment target may be selected in each of the frames in each ofthe swaths in the reticle instance that will be used as the firstreticle instance.

One such embodiment is shown in FIG. 5. In this embodiment, wafer 500includes a number of reticle instances formed thereon including reticleinstance 502, which may be used as the first of the multiple reticleinstances in the embodiments described herein. In this embodiment, thecomputer subsystem(s) (not shown in FIG. 5) may perform select alignmenttargets step 504 in which alignment targets are selected from each swathin the first reticle instance. In particular, as shown in FIG. 5, aninspection subsystem configured as described herein may scan the firstreticle instance in a number of swaths 506, including Swath 1 to SwathN. (Although the reticle instance is shown in FIG. 5 to be scanned in 4swaths that divide the reticle instance vertically, reticle instances onthe wafer described herein may be scanned in any suitable number ofswaths, e.g., depending on the reticle and die configuration and theinspection subsystem configuration.) In this manner, the inspectionsubsystem may generate a number of swaths of inspection data or outputfor the wafer. Selecting the alignment targets in step 504 may includeselecting alignment targets in at least one of the swaths (e.g., oneswath, some (not all) of the swaths, or all of the swaths) depending onWhich one or more of the swaths will be examined for repeater defects.In particular, the alignment targets may be selected for each of theswaths for which repeater analysis will be performed. In addition, thealignment targets may be independently selected for each of the swaths.For example, the alignment targets in one of the swaths may be selectedindependently of the alignment targets in another (or all others) of theswaths.

The number of alignment targets that are selected in each swath may varydepending on the number of frames that are in the swaths. For example,one alignment target may be selected in each of the frames in whicheverswath alignment targets are being selected. However, more than onetarget may also be selected in each frame. In general, the morealignment targets that are identified and selected for use in theembodiments described herein, the smaller the search range can be forrepeater analysis. In addition, there is no guarantee that a suitablealignment target can be found in each frame. If no alignment target canbe found for a particular frame, the normalized cross-correlation (oranother alignment method described herein) on the entire frame may beused to align reticle instances or the information for a neighboringframe can be used to align reticle instances.

The alignment targets may include any suitable alignment targets andpatterned features. A suitable alignment target may be an image patternthat satisfies certain criteria. For example, the alignment targets maybe selected to include patterned features that are unique in one or morecharacteristics (e.g., shape, size, orientation, grey level change,etc.) within some area in a frame such that they can be used foralignment with relatively high confidence. The alignment targets mayalso preferably include features that render them suitable for alignmentin two dimensions (x and y). In general, there are many ways to selectsuitable alignment targets within a frame of inspection output, and thealignment targets may be selected as described herein in any of thoseways. It is noted, however, that the embodiments described herein arepreferably performed without using design information (e.g., designdata) for the wafer since the design information may not always beavailable (e.g., for intellectual property reasons). In this manner, thealignment target selection described herein may be performed usingoutput (e.g., images) generated for the first reticle instance by theinspection subsystem (as opposed to using the design information toselect the alignment targets). The embodiments described hereintherefore provide the ability to achieve substantially high relativedefect location accuracy for repeater analysis without design data.

As shown in FIG. 5, the computer subsystem(s) may be configured toperform save alignment targets step 508. The alignment targets that areselected may be saved (or stored in one or more of the computer-readablestorage media described herein) a number of different ways. Unlessotherwise noted herein, the information for the alignment targets thathave been selected may include any available information for thealignment targets, but will most likely include at a minimum the swathcoordinates of the alignment targets, the frames in which the alignmenttargets are located, and the swaths in which the alignment targets arelocated. In this manner, the data for the alignment targets that issaved may look something like: Target(ID)=(alignment target swathcoordinates, frame ID, swath ID, . . . ). As such, the computersubsystem(s) may generate stored target information 510. The storedtarget information may then be used as described further herein.

In another embodiment, the output for the first of the frames used inthe aligning step is output for an alignment target in the first of theframes, the output for the corresponding others of the frames used inthe aligning step is output for alignment sites in the correspondingothers of the frames, and the computer subsystem(s) are configured forselecting alignment targets in the frames in the multiple swaths in thefirst of the multiple reticle instances, separating the selectedalignment targets into groups based on the multiple swaths in which theyare located such that each of the groups corresponds to fewer than allof the multiple swaths, and storing information for the selectedalignment targets in the groups into different portions of the one ormore computer subsystems based on which of the different portions of theone or more computer subsystems perform the detecting, aligning,determining, and applying for different ones of the groups,respectively. For example, the computer subsystem(s) may select thealignment targets as described further herein, and the computersubsystem(s) may save the targets into different image computer (IMC)nodes (not shown) included in the computer subsystem(s) and group thetargets by swath. In particular, the targets may be stored in the IMCnode that will process the swath of inspection output in which thetargets are located. In this manner, the IMC nodes may store only thealignment targets that they will need for other steps described herein.Such grouping and storing is also not limited to just IMC nodes, but canbe used for any of the other storage media described herein.

In this manner, as shown in FIG. 5, in one embodiment, the alignmenttargets selected from swath 1 may be stored as targets 1, which may beone group of the alignment targets, and alignment targets selected fromswath N may be stored as targets N, which may be another group ofalignment targets. Alignment target information may likewise be storedfor any other swaths for which alignment targets were selected. As such,different groups of alignment targets may be generated by the computersubsystem(s), and each of the different groups may correspond to one ofthe different swaths. Each of the different groups of targets may thenbe stored in the different IMC node that will be using the differentgroups of targets. For example, the group of targets 1 may be stored ina first IMC node that will process the inspection output in swath 1, andthe group of targets N may be stored in IMAC node N that will processthe inspection output in swath N. The information for the alignmenttargets in other groups may be stored in other IMC nodes in a similarmanner.

In some embodiments, the output for the first of the frames used in thealigning step is output for an alignment target in the first of theframes, the output for the corresponding others of the frames used inthe aligning step is output for alignment sites in the correspondingothers of the frames, and the one or more computer subsystems areconfigured for selecting alignment targets in the frames in the multipleswaths in the first of the multiple instances of the reticle from theoutput generated for the wafer by the detector while the inspectionsubsystem directs the generated energy to the wafer and the detectordetects the energy from the wafer for an inspection scan. In thismanner, the alignment target selection, which may be performed asdescribed further herein, may be performed during run time of a waferinspection. The embodiments described herein therefore provide theability to achieve substantially high relative defect location accuracyfor repeater analysis without a setup scan (since a setup scan is notneeded for alignment target selection). As such, the alignment targetselection performed as described herein may be runtime targetidentification for relative alignment to a first inspected reticleinstance. In other words, when inspecting the first reticle instance,alignment targets are selected from the first reticle instance. At leastone target per frame can be selected. Such alignment target selectionmay be further performed as described herein.

FIG. 6 shows a run time process that may be performed for any otherinspected reticle instance after the alignment targets have beenselected from the first reticle instance as described above. In FIG. 6,wafer 600 has a number of reticle instances formed thereon includingreticle instance 602, which may be used as the first of the multiplereticle instances as described herein, and reticle instance 608, whichmay be another inspected reticle instance on the wafer. As describedfurther above, first reticle instance 602 may be scanned therebygenerating a number of swaths 604 of output from which targets 606 areselected as described herein. The targets in this embodiment may beselected during the runtime of the inspection process and may be storedas described further herein on corresponding IMC nodes (not shown) ofthe computer subsystem(s). For example, targets 1 may be stored on IMCnode 1, . . . targets N may be stored on IMC node N, and so on. Whenother reticle instance 608 is then scanned thereby generating a numberof swaths 610, the output for alignment targets 606 may be aligned tothe output for alignment sites in corresponding frames and correspondingswaths 610 in alignment step 612. This alignment step may be performedas described further herein.

The results of the alignment step may then be used in transformcoordinates step 614, which may include determining different swathcoordinate offsets for each of the alignment sites, respectively, in theother reticle instances based on differences between swath coordinatesof the output for the alignment sites and swath coordinates of theoutput for the alignment target aligned thereto in the aligning step andapplying one of the different swath coordinate offsets to the swathcoordinates reported for the defects detected on the wafer, where whichof the different swath coordinate offsets is applied to the swathcoordinates reported for the defects is determined based on the othersof the multiple reticle instances in which the defects were detected. Inthis manner, the transform coordinates step 614 may transform swathcoordinates reported for the defects from swath coordinates in reticleinstance 608 to swath coordinates in first reticle instance 602. Thesesteps may be performed for all of the reticle instances that areinspected on the wafer.

In this manner, the embodiments described herein may perform a reticleinstance-swath coordinate transformation using runtime identifiedtargets. As described further herein, when any other reticle instance isinspected, an offset between the swath coordinates of the first and theinspected reticle instances for each frame (and therefore each swath)may be determined by aligning targets of the first reticle instance tothe inspected reticle instance. After any defect is detected, itslocation in the reticle instance-swath coordinates is transformed intothe reticle instance-swath coordinates of the first reticle instance. Inthis way, positions of defects in all reticle instances are representedin terms of the swath coordinates of the first reticle instance.

In a further embodiment, the output for the first of the frames used inthe aligning step is output for an alignment target in the first of theframes, the output for the corresponding others of the frames used inthe aligning step is output for alignment sites in the correspondingothers of the frames, and the computer subsystem(s) are configured forselecting alignment targets in the frames in the multiple swaths in oneof the multiple instances of the reticle from output generated for thewafer by the detector in a setup scan of only the one of the multipleinstances of the reticle performed before the detector of the inspectionsubsystem generates the output used to detect the defects on the wafer,generating a data structure containing information for the selectedalignment targets, and storing the data structure in a non-transitorycomputer-readable storage medium. The “one reticle instance” or “setupreticle instance” used for setup can be any reticle instance on thewafer. In this manner, the alignment targets can be selected and storedin a setup scan of the wafer. For example, if throughput is relativelycritical and target finding during inspection (runtime) is notacceptable, a setup scan can be used to select the targets offline. Suchalignment target selection may be performed as shown in FIG. 5. However,unlike the alignment target selection during inspection runtimedescribed above in which information for the selected alignment targetsmay be stored on the IMC nodes of the computer subsystem(s), when thealignment targets are selected during a setup scan, the information forthe alignment targets may be stored to offline storage. The offlinestorage may be, for example, a database in a memory medium that isaccessible to the computer subsystem(s) or one of the non-transitorycomputer-readable media described herein. In this manner, theembodiments described herein may include separate setup based alignmenttarget identification and offline storage of targets. The alignmenttarget selection performed during a setup phase of inspection mayotherwise be performed as described herein. For example, in a setupscan, alignment targets may be selected from one reticle instance. Atleast one target per frame can be selected. The targets are then savedinto an appropriate storage medium such as an offline database.

Alignment targets selected during a setup phase of inspection may beused for defect swath coordinate transformation as described furtherherein. For example, defect swath coordinate transformation using setupbased targets may be performed as shown in FIG. 6. However, unlike theruntime alignment target selection described above, in this embodiment,targets 606 may be stored in offline storage instead of on the IMC nodesof the computer subsystem(s). During inspection, an offset between theswath coordinates of the setup reticle instance and the inspectedreticle instance for each frame may be computed by aligning targets ofthe setup reticle instance to the image of the inspected reticleinstance, which may be performed as described further herein. After anydefect is detected, its location in the reticle instance-swathcoordinates of the reticle instance in which it was detected may betransformed into the reticle instance-swath coordinates of the setupreticle instance as described further herein. In this way, defects inall other reticle instances may be represented in terms of the swathcoordinates of the setup reticle instance.

In another embodiment, the output for the first of the frames used inthe aligning step is output for an alignment target in the first of theframes, the output for the corresponding others of the frames used inthe aligning step is output for alignment sites in the correspondingothers of the frames, and the one or more computer subsystems areconfigured for selecting alignment targets in the frames in the multipleswaths in one of the multiple instances of the reticle from outputgenerated for the wafer by the detector in a setup scan of only the oneof the multiple instances of the reticle performed before the detectorof the inspection subsystem generates the output used to detect thedefects on the wafer, generating a data structure containing onlylocation information for the selected alignment targets, and storing thedata structure in a non-transitory computer-readable storage medium. Inthis manner, the alignment targets can be selected and their locationscan be stored in a setup scan of the wafer. Only the target locationscan be saved during setup to reduce the database (or other datastructure) size. The embodiments described herein may, therefore, beconfigured for separate setup based alignment target identification andoffline storage of target locations. In a setup scan, alignment targetsare selected from “one reticle instance” or the “setup reticleinstance.” At least one target per frame can be selected. The targetlocation information may then be stored into an offline database or anyother suitable storage medium.

One such embodiment is shown in FIG. 7. Any reticle instance can beselected as the setup reticle instance. In FIG. 7, the first reticleinstance is selected as the setup reticle instance. In this embodiment,wafer 700 may include a number of reticle instances formed thereonincluding reticle instance 702, which may be used as the one of themultiple reticle instances in the embodiments described herein. In thisembodiment, the computer subsystem(s) (not shown in FIG. 7) may performselect alignment targets step 704 in which alignment targets areselected from each swath in the setup reticle instance. In particular,as shown in FIG. 7, an inspection subsystem configured as describedherein may scan the setup reticle instance in a number of swaths 706,including Swath 1 to Swath N. In this manner, the inspection subsystemmay generate a number of swaths of inspection data or output for thewafer. Selecting the alignment targets in step 704 may be performed asdescribed herein. The alignment targets may be configured as describedfurther herein.

As shown in FIG. 7, the computer subsystem(s) may be configured toperform save alignment target locations step 708. The locations of thealignment targets that are selected may be saved (or stored in one ormore of the computer-readable storage media described herein) in anumber of different ways. Unless otherwise noted herein, the locationinformation for the alignment targets that have been selected mayinclude any available location information for the alignment targets,but will most likely include at a minimum the swath coordinates of thealignment targets, the frame in which the alignment targets are located,and the swath in which the alignment targets are located. In thismanner, the data for the alignment targets that is saved may looksomething like: Target(ID)=(alignment target swath coordinates, frameID, swath ID, . . . ). As such, the computer subsystem(s) may generatestored target location information 710, which in this case includes onlylocation information. In particular, the alignment target locationinformation that is stored for the alignment targets in Swath 1 mayinclude Locations 1, . . . the alignment target location informationthat is stored for alignment targets in Swath N may include Locations N,etc. The stored target location information may then be used asdescribed further herein.

In one such embodiment, the one or more computer subsystems areconfigured for acquiring the output generated by the detector for theselected alignment targets in the multiple instances of the reticleduring inspection of the wafer based on only the location information.In this manner, targets (e.g., target images) can be created duringinspection based on the target locations. One such embodiment is shownin FIG. 8. In this figure, wafer 800 includes a number of reticleinstances including reticle instance 802, which is used as the setupreticle instance in this embodiment, and reticle instance 808, which isanother inspected reticle instance in this embodiment. As describedfurther herein, in a setup scan, reticle instance 802 may be scanned tothereby generate a number of swaths 804 of output for the reticleinstance. That output may then be used as described further herein toselect alignment targets, for which only the location information may bestored as stored location information 806.

In some such embodiments, the one or more computer subsystems areconfigured for separating the selected alignment targets into groupsbased on the multiple swaths in which they are located such that each ofthe groups correspond to fewer than all of the multiple swaths andstoring the acquired output for the selected alignment targets in thegroups into different portions of the one or more computer subsystemsbased on which of the different portions of the one or more computersubsystems perform the detecting, the aligning, the determining, and theapplying for different ones of the groups, respectively. For example,the location information for the selected alignment targets may bestored in offline storage based on the swath in which the alignmenttargets are located. In this manner, the alignment targets may begrouped by swath and then the location information for different groupsof the alignment targets may be stored into different portions of thecomputer subsystem(s) (e.g., based on which portion of the computersubsystem(s) will process the output generated for each swath). Thelocation information for the alignment targets may otherwise be storedas described further herein.

During inspection of the wafer, alignment target locations identified inreticle instance 802 may be scanned based on stored location information806, as shown in image target locations step 812. In this manner, imagetarget locations step 812 may include grabbing and storing targetpatches on the first reticle instance of multiple inspected reticleinstances. Reticle instance 808 may also be scanned during inspection ofthe wafer to thereby generate a number of swaths 810 for that reticleinstance. Alignment step 814 may then be performed as described furtherherein using the stored alignment target patches grabbed in step 812 andthe output generated for reticle instance 808 at the correspondingalignment sites in the corresponding frames and swaths. The results ofthe alignment step may then be used for transform coordinates step 816,which may be performed as described further herein, to thereby transformswath coordinates of defects detected in reticle instance 808 to swathcoordinates in reticle instance 802.

The embodiments described herein may therefore be configured for reticleinstance-swath coordinate transformation using setup-based targetlocations. During inspection, target patches (i.e., patch images, whichare relatively small images generated at specific locations) may begrabbed and stored on image computer nodes based on target locations.During target patch grabbing, only the locations of the alignmenttargets may be scanned for image grabbing. However, during target patchgrabbing, the entirety of the first reticle instance that is to beinspected may be scanned to thereby generate both images of the storedalignment target locations as well as output that will be used to detectdefects in the first reticle instance. An offset between the swathcoordinates of the first reticle instance and the inspected reticleinstance for each frame may be determined by aligning targets of thegrabbed images to the image of the inspected reticle instance. After anydefect is detected, its location in the reticle instance-swathcoordinates of the reticle instance in which it is detected istransformed into the reticle instance-swath coordinates of the firstreticle instance as described further herein. In this way, defects inall other reticle instances can be represented in terms of the swathcoordinates of the first reticle instance.

In some embodiments, the one or more computer subsystems are notconfigured to determine positions of the defects relative to the wafer.For example, none of the embodiments described herein include or requiredetermining positions of the defects relative to a reference point on awafer or other wafer. Instead, the only positions of the defects thatare determined in (or by) the embodiments described herein are swathcoordinates reported by the defect detecting step and the transformedswath coordinates determined by the applying step. Since the embodimentsdescribed herein were created specifically to address issues in repeateranalysis caused by relative defect location accuracy, which is improvedby the embodiments described herein by transforming swath coordinates ofdefects in one reticle instance to swath coordinates in another reticleinstance, no other (e.g., wafer relative) defects positions need to bedetermined by the embodiments described herein.

In another embodiment, the one or more computer subsystems areconfigured for repeating the aligning, the determining, and the applyingsteps for others of the frames in the multiple swaths in the first ofthe multiple instances of the reticle. For example, although someembodiments are described herein with respect to a first frame and afirst swath in the first reticle instance, the embodiments may performthe aligning, determining, and applying for other frames in other swathsin the first reticle instance. In other words, the embodiments describedherein may perform the aligning, determining, and applying steps forone, some (e.g., two or more), or all of the frames being inspected on awafer. In addition, the embodiments described herein may be performedfor one, some (e.g., two or more), or all of the defects detected on awafer regardless of the positions reported for the defects.

The embodiments described herein have a number of advantages over othermethods and systems for determining defect positions. For example, theembodiments described herein transform defect locations from all reticleinstances to common coordinates during inspection and significantlyincrease relative defect location accuracy. In an additional example,the swath-to-swath (reticle instance-to-reticle instance) offset isremoved from the defect locations. In particular, after swath offsetsare measured or determined, defect locations can be transformed from aswath in one reticle instance to the corresponding swath in the firstreticle instance. After transformation, the offsets between swaths andreticle instances are therefore removed. In this manner, the variation(about 0.1 pixel to about 1 pixel) of defect locations relative to onereticle instance-swath is much smaller than the variation (about 10pixels) of defect locations across multiple swaths. In another example,for repeater analysis, the search area reduction provided by theembodiments described herein may be 100× to 10,000× and search range(repeater tolerance) reduction provided by the embodiments describedherein is about 10× to about 100×. In an additional example, theembodiments described herein potentially reduce false repeaterssignificantly. In other words, the embodiments described herein canreduce the false repeater count for repeater analysis. Furthermore, theembodiments described herein are particularly advantageous fornon-context based inspection (non-CBI) and multi-die reticle use casesunlike other defect position determination methods like aligninginspection output to design data and standard reference die (SRD)methods. Moreover, unlike previously used defect position determinationmethods and systems, the embodiments described herein do not necessarilyrequire a setup scan and are easier to use.

More specifically, with respect to previously used SRD methods, theembodiments described herein and those previously used methods may becapable of the same relative defect location accuracy. The embodimentsdescribed herein and SRI) methods may also both align targets toinspection images during runtime, and some of the embodiments describedherein and SRD methods both save target locations into a database.However, unlike SRD methods and systems, the embodiments describedherein do not generate a golden reference image offline (of a whole die)that is used during inspection. In addition, unlike SRD methods andsystems, some of the embodiments described herein do not necessarilyrequire a setup scan. The embodiments described herein are thereforesimpler for development and ease of use than SRD methods and systems.Furthermore, SRD methods and systems and the embodiments describedherein are suitable for different use cases. In particular, SRD methodsand systems are suitable for single die reticle use cases, while theembodiments described herein are particularly suitable for multi-diereticles without design information.

With respect to previously used CBI methods, the embodiments describedherein and those previously used methods may both align targets to aninspection image during run time. In addition, like CBI methods, some ofthe embodiments described herein may save targets into a database.However, unlike previously used CBI methods and systems, the embodimentsdescribed herein do not require design information and no inspectionoutput to design data alignment is required. In addition, unlike CBImethods and systems, some of the embodiments described herein do notnecessarily require a setup scan. Additionally, unlike CBI methods andsystems, some of the embodiments described herein do not save alignmenttarget output (e.g., images) and instead only save alignment targetlocation information. Furthermore, the embodiments described hereinprovide potentially better relative defect location accuracy thanpreviously used CBI methods and systems. Moreover, CBI methods andsystems and the embodiments described herein are suitable for differentuse cases. In particular, CBI methods and systems are suitable formulti-die reticle with design information use cases, while theembodiments described herein are particularly suitable for multi-diereticles without design information.

The embodiments described herein also provide a simpler way to achievesubstantially high defect location accuracy for repeater analysiswithout sacrificing performance. The implementation is simpler and it issimpler for users to use than other existing approaches. Repeateranalysis is substantially important to reduce nuisance rate for the EUVprint check use case, which will be very likely adopted by advancedsemiconductor manufacturers in the next couple of years.

As set forth in U.S. Pat. No. 8,126,255 issued on Feb. 28, 2012 toBhaskar et al., which is incorporated by reference above as if fully setforth herein, context based inspection technology may include any of thecontext based inspection methods and systems described in U.S. patentapplication Ser. No. 11/561,735 by Kulkarni et al. filed on Nov. 20,2006, which published as U.S. Patent Application Publication No.2007/0156379 on Jul. 5, 2007, and which is incorporated by reference asif fully set forth herein.

The embodiments described herein also enable algorithms using multiplestreams of stored data to improve sensitivity. For example, in oneembodiment, the set of processor nodes is configured to detect defectson the wafer using multiple streams of image data stored in the arraysof the storage media. In this manner, the embodiments described hereincan be used to exploit memory coupled to the processor nodes to retaindata across wafer scans in order to improve defect detection withouthaving to transfer substantially large amounts of data between computingsystems for analysis.

In another embodiment, the set of processor nodes is configured todetect defects on the wafer using multiple streams of image data. In onesuch embodiment, one of the multiple streams includes the image datastored in the arrays of the storage media, and another of the multiplestreams includes image data generated by the detector during additionalscanning of the wafer. In some such embodiments, the scanning and theadditional scanning of the wafer are performed with one or moredifferent parameters of the inspection system. In this manner, theembodiments described herein can use stored image data (e.g., stored inthe arrays of the storage media as described further herein) formulti-scan applications such as multi-scan defect detection. Inaddition, for multi-scan defect detection, the stored data may be readback, frame-by-frame, into the VI column from the arrays of the storagemedia, aligned and combined at the pixel level for defect detection.Alignment of the stored image data at the pixel level may be performedas described in the U.S. patent application Ser. No. 11/561,735 byKulkarni et al. published as U.S. Patent Application Publication No.2007/0156379 on Jul. 5, 2007, which is incorporated by reference above.

In one embodiment, the set of processor nodes is configured to detectdefects on the wafer using the image data stored in the arrays of thestorage media by comparing a portion of the image data corresponding toa die on the wafer to another portion of the image data corresponding toa different die on the wafer. In one such embodiment, the portion of theimage data and the other portion of the image data are included in asingle stream of image data. In this manner, the set of processor nodesmay be configured to detect defects on the wafer using die-to-die typecomparisons. The portions of the image data that are compared to eachother may include image data included in a single stream of image data.

In a further embodiment, the set of processor nodes is configured todetect defects on the wafer using the image data stored in the arrays ofthe storage media by comparing a portion of the image data correspondingto a die on the wafer to a standard reference die and by comparing adifferent portion of the image data corresponding to the die on thewafer to a corresponding portion of the image data corresponding to adifferent die on the wafer. In this manner, the embodiments describedherein may be configured for “die-to-sparse standard reference diedetection.” For instance, die-to-sparse standard reference dieinspection may be performed at pre-defined locations by saving patchimages from a scan of the standard reference die at selected locations(e.g., potential repeater or systematic defect locations) and usingthese patch images to compare with corresponding locations on a test diewhile performing die-to-adjacent die inspections at other locations. Inparticular, the set of processor nodes may be configured to concurrently(in the same scan) perform random defect detection using die-to-adjacentdie comparison and perform systematic defect monitoring usingdie-to-stored standard reference patch images from pre-selected areas.The pre-selected areas for which die-to-stored standard reference patchimages may be used for defect detection may, therefore, include areas ofthe die that may present special cases or areas of particular interest(e.g., areas that include locations of potential systematic defects). Inaddition, the pre-selected areas for which the die-to-stored standardreference die comparison is used may be a relatively small area of thedie (e.g., about 1% of the pixels), and as such, the amount of memoryneeded to store the sparse standard reference die may be relativelysmall compared to that required for a standard reference image for theentire die.

The standard reference die may be generated in any suitable manner. Inone embodiment, the set of processor nodes is configured to generate astandard reference die using image data for two or more dies on one ormore wafers and to store the standard reference die in the arrays of thestorage media. For example, the standard reference die may be generatedusing data acquired for several dies on a wafer. Examples of methods forgenerating such a standard reference die are described in commonly ownedU.S. Patent Application Ser. No. 60/950,974 by Bhaskar et al. filed Jul.20, 2007 and Ser. No. 12/176,095 by Bhaskar et al. filed Jul. 18, 2008,which is incorporated by reference as if fully set forth herein. Theembodiments described herein may be configured to perform any step(s) ofany method(s) described in these patent applications.

In addition, although the embodiments described herein may be configuredto perform die-to-sparse standard reference die defect detection inwhich only a portion of a die on the wafer is compared to a standardreference die, the embodiments described herein may also oralternatively be configured to compare an entire die to a standardreference die for defect detection. For example, in one embodiment, theset of processor nodes is configured to perform wafer inspection bycomparing image data corresponding to a die on the wafer to a standardreference die, and the image data corresponding to the die on the waferand the standard reference die are stored in the arrays of the storagemedia. Therefore, the VI may be configured to perform die-to-standardreference die inspection offline. In another embodiment, the set ofprocessor nodes is configured to perform wafer inspection by comparing astandard reference die stored in the arrays of the storage media toimage data corresponding to a die on the wafer as the image datacorresponding to the die is received from the detector. Therefore, theVI may be configured to perform die-to-standard reference die inspectiononline (as the image data is generated using a physical wafer). Forexample, during die-to-standard reference die wafer inspection, the VIcan pull both streams in together, the stream of data for the wafer andthe standard reference die. In this manner, as the data is streaming infrom the inspection system, the streaming data can be compared to astored standard reference die on the VI.

In some such embodiments for die-to-sparse standard reference die defectdetection, the method shown in FIG. 4 can be generalized to a case inwhich we capture (within a node) patch images from a known good die froma known good reference wafer and then use these patch images to comparethe corresponding regions on all die of a test wafer being inspected.The number of standard reference patch images that can be saved dependson the memory capacity per inspection system node, the patch image sizesaved (e.g., 128 pixels by 128 pixels), and the geographicaldistribution of the standard reference patch images since each nodereceives a fraction of the die area. For example, certain locations on atest wafer can be inspected against the standard reference die to detectrepeater or systematic defect mechanisms while die-to-adjacent diedefect detection methods can be used for the rest of the wafer.

In some embodiments, the set of processor nodes is configured to comparethe image data for the wafer stored in the arrays of the storage mediawith image data for another wafer. In one such embodiment, the set ofprocessor nodes is configured to store image data for two full wafers onthe VI. The set of processor nodes may then designate one wafer as thetest wafer and the other as the reference wafer. In one such example, atest die on a test wafer may be compared to a stored standard referencedie on a reference wafer to detect defects on the test die. A referencedie on the reference wafer may also be compared to the stored standardreference die to detect defects on the reference die. The reference dieand the test die may be located in corresponding areas on the two wafers(e.g., the reference die and the test die may have substantially thesame coordinates on the two wafers). The defects detected on the testdie may also be compared with defects detected on the reference die. Theset of processor nodes may also be configured to manage the issuesrelated to having multiple references per test die for defectarbitration (i.e., to determine which wafer or which portion of a waferon which the defect is located).

In another such embodiment, the set of processor nodes is configured tostore a reference wafer on the VI. The set of processor nodes may alsobe configured to connect the VI to a “real” inspection system and tofeed the reference data from the VI to the real inspection system duringthe inspection process. The reference data may be fed from the VI to thereal inspection system at substantially the same rate at which the realinspection system acquires the test data. However, the reference datamay be fed from the VI to the real inspection system at a rate that isdifferent than that at which the test data is acquired (e.g., some ofthe reference data or test data can be buffered or the reference dataand the test data may be acquired at different resolutions and maytherefore be fed to the real inspection system at different rates).

In this manner, the set of processor nodes may be configured forinter-wafer comparisons. Once the wafer images are loaded, awafer-to-wafer comparison may be performed either on a single VI, two VIconnected to each other, or a VI connected to a real inspection system.As such, the embodiments described herein can exploit the storage mediadescribed herein to retain data across wafer scans to monitor wafersignatures at a substantially fine level of detail without having totransfer substantially large amounts of data between computing systemsfor analysis.

For example, in one embodiment, the set of processor nodes is configuredto perform wafer property signature analysis using the image data storedin the arrays of the storage media. In particular, the proposedarchitecture for wafer noise monitoring exploits stored image databetween scans to record and monitor noise at a substantially fine levelof detail (wafer/die/frame/region) without being limited by the imagecomputer system I/O bandwidth limitations. For example, wafer-to-wafercomparisons that may be performed by the embodiments described hereinallow for comparing one wafer with another at a much greater level ofdetail than merely comparing defect maps of different, wafers. Inparticular, properties of each frame of each die can be compared acrosstwo wafers or between a test wafer and a reference wafer to allow forthe detection of wafer-wide signatures that may be used to identifysystematic defect mechanisms in the wafer fabrication process. Inaddition, the properties of each frame may be determined as a functionof design context. For example, difference statistics per frame perdesign context may be determined for the results of a test die-to-storedstandard reference die comparison and for a reference die-to-storedstandard reference die comparison. These frame statistics may then becompared to compare the test wafer to the reference wafer. In thismanner, the set of processor nodes may be configured to identify and/oranalyze a signature in a wafer property to identify systematic defects.The set of processor nodes may also be configured to identify and/oranalyze a signature in a wafer property to detect macro-level defects.Wafer-to-wafer comparisons may also be performed by the embodimentsdescribed herein as described in commonly owned U.S. patent applicationSer. No. 11/561,735 by Kulkarni et al. published as U.S. PatentApplication Publication No. 2007/0156379 on Jul. 5, 2007 and Ser. No.11/561,659 by Zafar et al. published as U.S. Patent ApplicationPublication No. 2007/0288219 on Dec. 13, 2007, both of which were filedon Nov. 20, 2006, and both of which are incorporated by reference as iffully set forth herein.

Returning now to material that was not incorporated by reference to U.S.Pat. No. 8,126,255 issued on Feb. 28, 2012 to Bhaskar et al., each ofthe embodiments described herein may be further configured as describedherein. For example, two or more of the embodiments described herein maybe combined into one single embodiment.

Another embodiment relates to a computer-implemented method fortransforming positions of defects detected on a wafer. The methodincludes detecting defects on a wafer by applying a defect detectionmethod to output generated for the wafer by a detector of an inspectionsubsystem, which is configured as described further herein. Positions ofthe defects are reported by the defect detection method in swathcoordinates. The output generated by the detector of the inspectionsubsystem includes multiple swaths of frames of output for each ofmultiple dies on the wafer, and each of multiple instances of a reticleprinted on the wafer includes at least two instances of the multipledies.

The method also includes aligning the output for a first of the framesin a first of the multiple swaths in a first of the multiple dies in afirst of the multiple instances of the reticle printed on the wafer tothe output for corresponding others of the frames in correspondingothers of the multiple swaths in corresponding others of the multipledies in others of the multiple instances of the reticle printed on thewafer. In addition, the method includes determining different swathcoordinate offsets for each of the frames, respectively, in the othersof the multiple instances of the reticle based on differences betweenswath coordinates of the output for the frames and swath coordinates ofthe output for the first of the frames aligned thereto in the aligningstep.

The method further includes applying one of the different swathcoordinate offsets to the swath coordinates reported for the defectsdetected on the wafer, Where which of the different swath coordinateoffsets is applied to the swath coordinates reported for the defects isdetermined based on the others of the multiple instances of the reticlein which the defects were detected, thereby transforming the swathcoordinates reported for the defects from swath coordinates in theothers of the multiple instances of the reticle to swath coordinates inthe first of the multiple instances of the reticle. The detecting, thealigning, the determining, and the applying are performed by one or morecomputer subsystems coupled to the inspection subsystem.

Each of the steps of the method may be performed as described furtherherein. The method may also include any other step(s) that can beperformed by the inspection subsystem and/or computer subsystem(s) orsystem(s) described herein. The steps of the method are performed by oneor more computer subsystems, which may be configured according to any ofthe embodiments described herein. In addition, the method describedabove may be performed by any of the system embodiments describedherein.

An additional embodiment relates to a non-transitory computer-readablemedium storing program instructions executable on a computer system forperforming a computer-implemented method for transforming positions ofdefects detected on a wafer. One such embodiment is shown in FIG. 9. Inparticular, as shown in FIG. 9, non-transitory computer-readable medium900 includes program instructions 902 executable on computer system 904.The computer-implemented method may include any step(s) of any method(s)described herein.

Program instructions 902 implementing methods such as those describedherein may be stored on computer-readable medium 900. Thecomputer-readable medium may be a storage medium such as a magnetic oroptical disk, a magnetic tape, or any other suitable non-transitorycomputer-readable medium known in the art.

The program instructions may be implemented in any of various ways,including procedure-based techniques, component-based techniques, and/orobject-oriented techniques, among others. For example, the programinstructions may be implemented using ActiveX controls, C++ objects,JavaBeans, Microsoft Foundation Classes (“MFC”), SSE (Streaming SIMDExtension) or other technologies or methodologies, as desired.

Computer system 904 may be configured according to any of theembodiments described herein.

All of the methods described herein may include storing results of oneor more steps of the method embodiments in a computer-readable storagemedium. The results may include any of the results described herein andmay be stored in any manner known in the art. The storage medium mayinclude any storage medium described herein or any other suitablestorage medium known in the art. After the results have been stored, theresults can be accessed in the storage medium and used by any of themethod or system embodiments described herein, formatted for display toa user, used by another software module, method, or system, etc. Forexample, the one or more computer subsystem(s) may output informationfor the defects identified as repeaters to a reticle repair system, andthe reticle repair system may use the information for the defectsidentified as repeaters to perform a repair process on the reticle tothereby eliminate the defects on the reticle.

Further modifications and alternative embodiments of various aspects ofthe invention will be apparent to those skilled in the art in view ofthis description. For example, methods and systems for transformingpositions of defects detected on a wafer are provided. Accordingly, thisdescription is to be construed as illustrative only and is for thepurpose of teaching those skilled in the art the general manner ofcarrying out the invention. It is to be understood that the forms of theinvention shown and described herein are to be taken as the presentlypreferred embodiments. Elements and materials may be substituted forthose illustrated and described herein, parts and processes may bereversed, and certain features of the invention may be utilizedindependently, all as would be apparent to one skilled in the art afterhaving the benefit of this description of the invention. Changes may bemade in the elements described herein without departing from the spiritand scope of the invention as described in the following claims.

What is claimed is:
 1. A system configured to transform positions ofdefects detected on a wafer, comprising: an inspection subsystemcomprising at least an energy source and a detector, wherein the energysource is configured to generate energy that is directed to a wafer,wherein the detector is configured to detect energy from the wafer andto generate output responsive to the detected energy, and wherein theoutput comprises multiple swaths of frames of output for each ofmultiple instances of a reticle printed on the wafer; and one or morecomputer subsystems configured for: detecting defects on the wafer byapplying a defect detection method to the output generated by thedetector, wherein positions of the defects are reported by the defectdetection method in swath coordinates; aligning the output for a setupframe in a setup swath in a setup reticle instance to the output for theframes corresponding to the setup frame in the multiple swathscorresponding to the setup swath in the multiple instances of thereticle printed on the wafer; determining different swath coordinateoffsets for each of the frames, respectively, in the multiple instancesof the reticle based on differences between swath coordinates of theoutput for the frames and swath coordinates of the output for the setupframe aligned thereto in the aligning step; and applying one of thedifferent swath coordinate offsets to the swath coordinates reported forthe defects detected on the wafer, wherein which of the different swathcoordinate offsets is applied to the swath coordinates reported for thedefects is determined based on the multiple instances of the reticle inwhich the defects were detected, thereby transforming the swathcoordinates reported for the defects from swath coordinates in themultiple instances of the reticle to swath coordinates in the setupreticle instance.
 2. The system of claim 1, wherein the setup reticleinstance is selected from the multiple instances of the reticle printedon the wafer, and wherein the setup reticle instance is scanned first bythe inspection subsystem in an inspection scan.
 3. The system of claim1, wherein the setup reticle instance is selected from all of themultiple instances of the reticle printed on the wafer.
 4. The system ofclaim 1, wherein the setup reticle instance is selected from themultiple instances of the reticle printed on the wafer, and wherein thesetup reticle instance is not scanned first by the inspection subsystemin an inspection scan.
 5. The system of claim 1, wherein each of themultiple instances of the reticle printed on the wafer comprises atleast two instances of multiple dies, and wherein said aligningcomprises aligning the output for the setup frame in the setup swath ina setup die in the setup reticle instance to the output for the framescorresponding to the setup frame in the multiple swaths corresponding tothe setup swath in the multiple dies corresponding to the setup die inthe multiple instances of the reticle printed on the wafer.
 6. Thesystem of claim 1, wherein the setup reticle instance is printed on adifferent wafer.
 7. The system of claim 6, wherein the defect detectionmethod comprises comparing the output generated by the detector for thewafer to the output generated for the setup reticle instance alignedthereto for wafer-to-wafer inspection.
 8. The system of claim 1, whereinthe one or more computer subsystems are further configured forperforming said aligning, said determining, and said applying withoutdesign information for devices being formed on the wafer.
 9. The systemof claim 1, wherein the one or more computer subsystems are notconfigured to perform any steps using design information for devicesbeing formed on the wafer.
 10. The system of claim 1, wherein the one ormore computer subsystems are further configured for determining if thedefects are repeater defects based on the transformed swath coordinatesfor the defects.
 11. The system of claim 1, wherein the one or morecomputer subsystems are further configured for determining if thedefects are caused on the wafer by the reticle used to print patternedfeatures on the wafer based on the transformed swath coordinates for thedefects.
 12. The system of claim 1, wherein the one or more computersubsystems are further configured for determining if the defects arecaused on the wafer by the reticle used to print patterned features onthe wafer based on the transformed swath coordinates for the defects,and wherein the reticle is an extreme ultraviolet reticle.
 13. Thesystem of claim 1, wherein the output for the setup frame used in thealigning step is output for an alignment target in the setup frame,wherein the output for the frames corresponding to the setup frame usedin the aligning step is output for alignment sites in the framescorresponding to the setup frame, wherein the one or more computersubsystems are further configured for selecting alignment targets insetup frames in the setup swath in the setup reticle instance, andwherein said selecting the alignment targets comprises selecting atleast one of the alignment targets in each of the setup frames in thesetup swath in the setup reticle instance.
 14. The system of claim 1,wherein the output for the setup frame used in the aligning step isoutput for an alignment target in the setup frame, wherein the outputfor the frames corresponding to the setup frame used in the aligningstep is output for alignment sites in the frames corresponding to thesetup frame, and wherein the one or more computer subsystems are furtherconfigured for selecting alignment targets in setup frames in setupswaths in the setup reticle instance, separating the selected alignmenttargets into groups based on the setup swaths in which they are locatedsuch that each of the groups corresponds to fewer than all of the setupswaths, and storing information for the selected alignment targets inthe groups into different portions of the one or more computersubsystems based on which of the different portions of the one or morecomputer subsystems perform said detecting, said aligning, saiddetermining, and said applying for different ones of the groups,respectively.
 15. The system of claim 1, wherein the setup reticleinstance is selected from the multiple instances of the reticle printedon the wafer, wherein the output for the setup frame used in thealigning step is output for an alignment target in the setup frame,wherein the output for the frames corresponding to the setup frame usedin the aligning step is output for alignment sites in the framescorresponding to the setup frame, and wherein the one or more computersubsystems are further configured for selecting alignment targets insetup frames in setup swaths in the setup reticle instance from theoutput generated for the wafer by the detector while the inspectionsubsystem directs the generated energy to the wafer and the detectordetects the energy from the wafer for an inspection scan.
 16. The systemof claim 1, wherein the setup reticle instance is selected from themultiple instances of the reticle printed on the wafer, wherein theoutput for the setup frame used in the aligning step is output for analignment target in the setup frame, wherein the output for the framescorresponding to the setup frame used in the aligning step is output foralignment sites in the frames corresponding to the setup frame, andwherein the one or more computer subsystems are further configured forselecting alignment targets in setup frames in setup swaths in the setupreticle instance from output generated for the wafer by the detector ina setup scan of only the setup reticle instance performed before thedetector of the inspection subsystem generates the output used to detectthe defects on the wafer, generating a data structure containinginformation for the selected alignment targets, and storing the datastructure in a non-transitory computer-readable storage medium.
 17. Thesystem of claim 1, wherein the setup reticle instance is selected fromthe multiple instances of the reticle printed on the wafer, wherein theoutput for the setup frame used in the aligning step is output for analignment target in the setup frame, wherein the output for the framescorresponding to the setup frame used in the aligning step is output foralignment sites in the frames corresponding to the setup frame, andwherein the one or more computer subsystems are further configured forselecting alignment targets in setup frames in setup swaths in the setupreticle instance from output generated for the wafer by the detector ina setup scan of only the setup reticle instance performed before thedetector of the inspection subsystem generates the output used to detectthe defects on the wafer, generating a data structure containing onlylocation information for the selected alignment targets, and storing thedata structure in a non-transitory computer-readable storage medium. 18.The system of claim 17, wherein the one or more computer subsystems arefurther configured for acquiring the output generated by the detectorfor the selected alignment targets in the setup reticle instance duringinspection of the wafer based on only the location information.
 19. Thesystem of claim 18, wherein the one or more computer subsystems arefurther configured for separating the selected alignment targets intogroups based on the setup swaths in which they are located such thateach of the groups corresponds to fewer than all of the setup swaths andstoring the acquired output for the selected alignment targets in thegroups into different portions of the one or more computer subsystemsbased on which of the different portions of the one or more computersubsystems perform said detecting, said aligning, said determining, andsaid applying for different ones of the groups, respectively.
 20. Thesystem of claim 1, wherein said aligning comprises target-basedalignment of the output for the setup frame to the output for the framescorresponding to the setup frame in the multiple instances of thereticle printed on the wafer.
 21. The system of claim 1, wherein saidaligning comprises feature-based alignment of the output for the setupframe in the setup reticle instance to the output for the framescorresponding to the setup frame in the multiple instances of thereticle printed on the wafer.
 22. The system of claim 1, wherein saidaligning comprises normalized cross correlation-based alignment of theoutput for the setup frame in the setup reticle instance to the outputfor the frames corresponding to the setup frame in the multipleinstances of the reticle printed on the wafer.
 23. The system of claim1, wherein said aligning comprises Fast Fourier transform-basedalignment of the output for the setup frame in the setup reticleinstance to the output for the frames corresponding to the setup framein the multiple instances of the reticle printed on the wafer.
 24. Thesystem of claim 1, wherein said aligning comprises sum of squareddifference-based alignment of the output for the setup frame in thesetup reticle instance to the output for the frames corresponding to thesetup frame in the multiple instances of the reticle printed on thewafer.
 25. The system of claim 1, wherein the one or more computersubsystems are not configured to determine positions of the defectsrelative to the wafer.
 26. The system of claim 1, wherein the one ormore computer subsystems are further configured for repeating saidaligning, said determining, and said applying for other setup frames insetup swaths in the setup reticle instance.
 27. The system of claim 1,wherein the energy directed to the water comprises light, and whereinthe energy detected from the wafer comprises light.
 28. The system ofclaim 1, wherein the energy directed to the wafer comprises electrons,and wherein the energy detected from the wafer comprises electrons. 29.A non-transitory computer-readable medium, storing program instructionsexecutable on a computer system for performing a computer-implementedmethod for transforming positions of defects detected on a wafer,wherein the computer-implemented method comprises: detecting defects ona wafer by applying a defect detection method to output generated forthe wafer by a detector of an inspection subsystem, wherein positions ofthe defects are reported by the defect detection method in swathcoordinates, wherein the inspection subsystem comprises at least anenergy source and the detector, wherein the energy source is configuredto generate energy that is directed to the wafer, wherein the detectoris configured to detect energy from the wafer and to generate the outputresponsive to the detected energy, and wherein the output comprisesmultiple swaths of frames of output for each of multiple instances of areticle printed on the wafer; aligning the output for a setup frame in asetup swath in a setup reticle instance to the output for the framescorresponding to the setup frame in the multiple swaths corresponding tothe setup swath in the multiple instances of the reticle printed on thewafer; determining different swath coordinate offsets for each of theframes, respectively, in the multiple instances of the reticle based ondifferences between swath coordinates of the output for the frames andswath coordinates of the output for the setup frame aligned thereto inthe aligning step; and applying one of the different swath coordinateoffsets to the swath coordinates reported for the defects detected onthe wafer, wherein which of the different swath coordinate offsets isapplied to the swath coordinates reported for the defects is determinedbased on the multiple instances of the reticle in which the defects weredetected, thereby transforming the swath coordinates reported for thedefects from swath coordinates in the multiple instances of the reticleto swath coordinates in the setup reticle instance.
 30. Acomputer-implemented method for transforming positions of defectsdetected on a wafer, comprising: detecting defects on a wafer byapplying a defect detection method to output generated for the wafer bya detector of an inspection subsystem, wherein positions of the defectsare reported by the defect detection method in swath coordinates,wherein the inspection subsystem comprises at least an energy source andthe detector, wherein the energy source is configured to generate energythat is directed to the wafer, wherein the detector is configured todetect energy from the wafer and to generate the output responsive tothe detected energy, and wherein the output comprises multiple swaths offrames of output for each of multiple instances of a reticle printed onthe wafer; aligning the output for a setup frame in a setup swath in asetup reticle instance to the output for the frames corresponding to thesetup frame in the multiple swaths corresponding to the setup swath inthe multiple instances of the reticle printed on the wafer; determiningdifferent swath coordinate offsets for each of the frames, respectively,in the multiple instances of the reticle based on differences betweenswath coordinates of the output for the frames and swath coordinates ofthe output for the setup frame aligned thereto in the aligning step; andapplying one of the different swath coordinate offsets to the swathcoordinates reported for the defects detected on the wafer, whereinwhich of the different swath coordinate offsets is applied to the swathcoordinates reported for the defects is determined based on the multipleinstances of the reticle in which the defects were detected, therebytransforming the swath coordinates reported for the defects from swathcoordinates in the multiple instances of the reticle to swathcoordinates in the setup reticle instance, and wherein said detecting,said aligning, said determining, and said applying are performed by oneor more computer subsystems coupled to the inspection subsystem.